1. Field of the Invention
The present invention relates generally to the field of textile printing apparatuses and more particularly, to a multi-head, carousel-type textile printing press having a vertically pivotal print head.
2. Related Art
Multi-station screen printing devices enable small printing shops to screen-print designs in multiple colors on articles such as shirts, jackets, and posters, to name but a few possible items. The substrate to be printed is supported on a flat surface called a platen while a number of print heads, each containing a different color of the design, are aligned with the platens for printing purposes. The platens are arrayed around a circle and supported by a sturdy base and pivot relative to the base for alignment with each of the separate print heads.
The print heads, on the other hand, while also being arrayed about a circle, are on some machines fixedly mounted relative to the base and the platens are rotated into position beneath each print head for printing each separate color. To print a multi-color design, each of the platens is in turn aligned with a particular print head to apply a particular color ink and is subsequently brought into contact with the print head, generally by raising the platens, whereupon the screen printing process for that particular color is performed on the article. The platen bearing the substrate is then rotated to the next print head to apply the next ink color. It follows that the number of print heads determines the number of different colors that can be combined to produce a printed design.
However, in the typical configuration for such machines there are usually fewer print heads than the number of platens for supporting the substrates, or workpieces. For example, on a printing machine having six platens there are at most five print heads. The reason for omitting one or more print head is to make it easier to add and remove substrates from the platens. The range of motion of the platens relative to the print heads is kept short in order to speed up the overall process of printing, since with a shorter range of motion the platens can move to each print head more quickly. Given this short range of motion, it is very difficult to add or remove the item to be printed from the platen when the platen is aligned with a print head. The solution therefore has been to omit one of the print heads so that the machine operator has unobstructed access to one of the platens.
The practical result of this configuration, though, is that a customer who wants to have six-color printing capability must purchase a machine with eight or more platens (similarly, a customer desiring four-color printing capability must buy a six-platen machine, etc.). However, the addition of more platens to a printing machine increases the cost and size of the machine, while many smaller print shops cannot afford the higher cost and may not have the additional space needed for the larger machine.
In another style of screen printing machine the print heads are mounted on pivoting arms, which pivot upwards between screening steps in order to allow the platens to rotationally change positions. As with the platens on the fixed head machines, the range of motion of the pivoting heads is limited in order to increase the overall speed of the screen printing process. Again, the limited range of motion of the pivoting print heads makes it difficult to add and remove articles from the platen, with the result that pivoting head printing machines also have at least one fewer print head than the number of platens, to allow unimpeded access to at least one of the platens.
What is needed is a screen printing apparatus that maximizes the number of individual colors that can be printed while minimizing the cost and size of the machine. Such an apparatus preferably allows easy addition and removal of the substrate material while maintaining a high degree of alignment between colors and rapid turnover of substrate articles, such as t-shirts, towels, banners and the like.